misleading doc string

[alexsquires]

    def save(self, filename: str):
        """
        Save the Analyzer object as a HDF5 file.

        :param filename: Name for the file, no file extension is required and if one if given it is replaced with .hdf.
        """

This doc strings is explicit in saying no extension is required, but if .hdf is not given, it errors out. I considered pushing a fix but then was not sure what the intended behaviour is.

[arm61]

On reading this issue, I was also confused. I thought that I had included the behaviour to if another file extension (or no extension) is given then it will automatically make it .hdf but I see now that that isn't the case. I am happy to take a PR that either fixes the docstring or adds functionality (whichever you think is more intuitive).